Palletized loads are often loaded and unloaded using a plurality of carriages that alternate between two positions on a continuous looped track, which may be either in a horizontal plane (like a racetrack) or in a vertical plane (like a ferris wheel). While both these lay outs are relatively simple mechanically, they consume a relatively large amount of floor space. Accordingly, a need has been apparent for apparatus for alternating a plurality of carriages between two positions that would consume less floor space, even at the cost of some increase in the complexity of the mechanisms involved.